Method and system for producing synthetic gas from biomass by high temperature gasification

ABSTRACT

A method and a system for producing synthetic gas from biomass by high temperature gasification, including: feeding raw material, carbonizing, pulverizing the charcoal, and transporting charcoal powder to the gasification furnace for gasification. A heat source for the carbonizing is achieved by a direct combustion reaction between external combustible gas and external oxygen in a carbonization furnace. The heat emitted from the reaction being directly provided to the necessary heat of biomass pyrolysis, and yielding pyrolysis gas and charcoal from carbonization furnace.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Patent ApplicationNo. PCT/CN2009/074712, with an international filing date of Oct. 30,2009, designating the United States, now pending, and further claimspriority benefits to Chinese Patent Application No. 200810236638.X,filed Dec. 1, 2008. The contents of all of the aforementionedapplications, including any intervening amendments thereto, areincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to the production of synthetic gas, and moreparticularly to a method and a system for producing synthetic gas frombiomass by high temperature gasification.

2. Description of the Related Art

Biomass, an organic matter generated by plants through photosynthesis,has wide sources and large available quantity. It can be transformedinto clean gas or liquid fuel for power generation and producingindustrial raw materials and chemical products. As energy it is cleanand renewable with zero emission of carbon dioxide.

There are many methods for transforming biomass into clean gas or liquidfuel, among which biomass gasification technology can adapt to a varietyof species and has good expansibility. The gasification of biomass is athermochemical process, i.e., biomass reacts with a gasification agent(such as air, oxygen, vapor, carbon dioxide, etc.) under hightemperature to produce a mixed gas consisting of carbohydrate containingcarbon, hydrogen, and oxygen. The mixed gas is named synthetic gas. Thecomponents of the synthetic gas are decided by the species of usedbiomass, the type of the gasification agent, the reaction conditions,and the structure of a gasifier used therein. The objectives ofgasification is, on the one hand, to minimize the consumption ofmaterials and the gasification agent, as well as the tar content in thesynthesis gas, and on the other hand, to maximize the gasificationefficiency and the efficiency of carbon conversion, as well as theactive ingredient (CO and H₂) content in the synthesis gas. Theobjectives are decided by the type of the used gasifier, the type of thegasification agent, the particle size of the biomass, the gasificationpressure and temperature, and moisture and ash of the biomass, etc.

Conventional gasifier is in the form of a fixed bed, a fluidized bed, oran entrained flow bed. The fixed bed has a simple structure and flexibleoperating mode, and is easy for practice. Solid materials have a longretaining time in the bed, the efficiency of carbon conversion is high,the operating load is wide (changeable between 20 and 110%). However,the temperature in the fixed bed is nonuniform, the heat exchange effectis poor, the synthetic gas has a low heating value, and a large amountof tar is produced; the fluidized bed is convenient for materialaddition and ash release, and the temperature is uniform and easy foradjustment. However, it is sensitive to the characteristics of rawmaterials. If the adhesion, thermal stability, moisture content, or ashmelting point of raw materials changes, the operation will becomeabnormal. Furthermore, the synthetic gas has a large amount of tar.Since a large amount of tar is produced in the fixed bed and thefluidized bed, a tar cracking unit and purification equipment must beinstalled, which results in a complicated process; the entrained flowbed has a high and uniform operating temperature, good amplificationcharacteristics, and particularly suitable for large-scaleindustrialization. Tar is cracked completely. However, the entrainedflow bed has a strict requirement on particle size of raw materials.Based on current grinding technology, there is no way to grind biomasshaving much cellulose to a size suitable for the entrained flow bed. Sothe entrained flow bed cannot be used for gasification of biomass.Nowadays, tar cracking and pretreatment of biomass prior to gasificationare tough problems for the development of biomass gasification. However,there are some limitations in the method and system for producingsynthetic gas of current technology: 1). when gasification, the carboncontent of the slag and ash is high, and combustion products (mainly CO₂and H₂O) are directly discharged, resulting in low gasificationefficiency and low efficiency of carbon conversion; 2). the content oftar is high in gas, which is easy to produce wastewater including focaland affect the normal operation of the equipment; 3). the temperature ofthe reactor is nonuniform; 4). in the industrial method, heating by thegasifier or cycled synthetic gas has hidden danger, the heating rate ofpyrolysis is very slow, material consumption is high, and thereby thetotal gasification efficiency is low; 5). the charcoal powdertransportation system is complicated. From the above mentioned methods,conventional gasification, whether from biomass or from solidcarbon-containing materials, cannot produce synthetic gas with highefficiency and low cost. Although the technology of independentpyrolysis and gasification can adapt to a variety of biomass and reducethe content of tar in synthetic gas, shortcomings such as nonuniformtemperature, large investment in equipment for waste heat recovery, highmaterial consumption, low gasification efficiency, and low carbonconversion rate limit the application of biomass gasification inindustry. Particularly, there is no effective method for gasifyingbiomass applied to an entrained flow bed.

SUMMARY OF THE INVENTION

In view of the above-described problems, it is one objective of theinvention to provide a method and a system for producing synthetic gasfrom biomass by high temperature gasification that has high efficiencyand low cost.

The invention is implemented as follows:

To achieve the above objectives, in accordance with one embodiment ofthe invention, there is provided a method for producing synthetic gasfrom biomass by high temperature gasification that has high efficiencyand low cost, the method comprising feeding raw material, carbonizing,pulverizing the charcoal, and transporting charcoal powder to thegasification furnace for gasification, wherein a heat source for thecarbonizing is achieved by a direct combustion reaction between externalcombustible gas and external oxygen in a carbonization furnace, the heatemitted from the reaction being directly provided to the necessary heatof biomass pyrolysis, and yielding pyrolysis gas and charcoal fromcarbonization furnace.

In a class of this embodiment, the temperature of carbonization furnaceis controlled at between 400° C. and 600° C. by adjusting the amount ofoxygen; the temperature of a burner nozzle of the carbonization furnaceis controlled at between 1200° C. and 1800° C. by adjusting the inputamount of the external combustible gas at between more than 1 and lessthan 5 times that required for a complete combustion with the externaloxygen.

In a class of this embodiment, the optical temperature of carbonizationfurnace is controlled at between 450° C. and 550° C. by adjusting theinput amount of the external oxygen and adjusting the input amount ofthe external combustible gas at between 1.5 and 3 times that requiredfor a complete combustion with the external oxygen.

In a class of this embodiment, prior to pulverizing, the charcoal isreduced to a normal pressure by a decompression feeding system ofcharcoal, pulverized into powders, and transported to a superchargingfeeding system of charcoal powder by normal pressure transport gas.

In a class of this embodiment, the pyrolysis gas produced bycarbonization furnace transports the charcoal powder to the gasifier;the ratio of solid to gas in the transportation pipe for charcoal powderis controlled at between 0.03 and 0.45 m³/m³ by adjusting the amount ofpyrolysis gas for transportation.

In a class of this embodiment, further comprises fluidizing during thetransportation of the charcoal powder, a fluidizing gas being theexternal combustible gas.

In a class of this embodiment, an outlet of the pyrolysis gas isdisposed on the top of the carbonization furnace and connected to thegasifier, a filter is disposed at the outlet of the pyrolysis gas, and apurge gas of the filter is the external combustible gas.

In accordance with another embodiment of the invention, there isprovided a system for producing synthetic gas from biomass by hightemperature gasification that has high efficiency and low cost, thesystem comprising a supercharging feeding system of biomass; acarbonization furnace having at least a burner nozzle; a pulverizingsystem; a gasifier; a pneumatic conveying system; and a plurality ofconnecting pipes thereof; the burner nozzle of the carbonization furnaceis connected to an external combustible gas pipe and an external oxygenpipe respectively.

In a class of this embodiment, from a charcoal outlet of thecarbonization furnace to the gasifier, a charcoal cooler, adecompression feeding system of charcoal, a pulverizer, and asupercharging feeding system of charcoal powder are disposedsequentially.

In a class of this embodiment, an outlet of the pyrolysis gas isdisposed on the top of the carbonization furnace and connected to thegasifier, a filter is disposed at the outlet of the pyrolysis gas, andthe connector of a purge gas of the filter is connected to a pipeline ofan external combustible gas.

Advantages of the Invention are Summarized Below:

1. The carbonization furnace is heated by a direct combustion betweenexternal combustible gas and external oxygen. The external combustiblegas is natural gas or exhaust gas containing hydrocarbon produced byother systems. The heating technology of the carbonization furnace inthe invention has the following three features: 1). the combustion gasis provided by external system; 2). the heat for the carbonization isproduced by a direct combustion between external combustible gas andexternal oxygen by using the chemical energy of the combustion gas; 3).due to direct combustion, the heating effect of the carbonizationfurnace is very good so that the carbonization process can be achievedquickly.

In the invention, external combustible gas and external oxygen are used,and by adjusting the proportion thereof, the temperature of thecarbonization furnace, the temperature of the burner nozzle of thecarbonization furnace, and the heating rate can be controlledeffectively. The invention has achieved the following objectives: a) toprovide heat for the carbonization of biomass by a direct combustionbetween the external combustible gas and oxygen; b) if the externalcombustible gas is excess, the excess part can be used as inert gas toabsorb heat so as to reduce the temperature of the burner nozzle of thecarbonization furnace; however, if real inert gas having no hydrocarbonis introduced to reduce the temperature of the burner nozzle of thecarbonization furnace, a large amount of inert gas will enter thegasification system, which means the working efficiency of the systemand the quality of the synthetic gas will decrease significantly; c)since the combustible gas is excess, only part of combustible gas isconsumed, the excess gas will be consumed in the gasifier, whichimproves the efficiency of energy utilization. Therefore, theintroduction of external combustible gas can improve the gasificationefficiency, reduce the oxygen consumption of the synthetic gas, andenhance the energy conversion rate of the system. Compared with themethod for producing synthetic gas by combined cycle gasification, inthe invention, the gasification efficiency has been increased by morethan 1%, and the oxygen consumption (the consumed oxygen (mole) forproducing 1 mole of CO and H₂) is reduced to less than 0.3 mol/mol.

2. The method according to the present invention uses pyrolysis gas todeliver charcoal powder. In conventional dry coal gasification, inertgas (CO₂ or N₂) is used as transport gas. The introduction of inert gasresults in low gasification efficiency and high oxygen consumption. Inthe invention, the charcoal powder is transported by pyrolysis gas, theoxygen consumption is decreased by between 10% and 20%, and thegasification efficiency is increased by between 5% and 10%.

3. The method according to the present invention adopts combustible gasto fluidize the charcoal powder. That the combustible gas fluidizescharcoal powder can avoid the blocking during transporting charcoalpowder, avoid introduction of inert gas which will result in low qualityof synthetic gas and low gasification efficiency, and also avoid thecondensation of the pyrolysis gas resulted from the entrance ofpyrolysis gas into the supercharging feeding system of charcoal powder.

4. The method according to the present invention uses combustible gas asthe equipment purging gas during its normal operation. That the externalcombustible gas is used as purge gas of the filter can avoid theintroduction of inert gas and improve the quality of the synthetic gas.Conventional coal gasification system uses the inert gas as purge gas,if the purge frequency is too high so that more inert gas will beintroduced and result in low quality of synthetic gas.

5. The method according to the present invention adopts the technologyof raw material depressurized feeding and atmospheric pressure charcoalmilling. Compared with the high-pressure milling technology adopted bythe combined-cycle high-temperature gasification method for producingsynthetic gas from biomass proposed, conventional superchargingpulverization is feasible theoretically, but there are many technicaldifficulties for practice, such as high pressure sealing and safety. Inthe invention, the decompression feeding of charcoal and pulverizationat normal pressure is safe and easy for practice.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a system and process for producingsynthetic gas from biomass by high temperature gasification according toone embodiment of the invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention is described herein below with reference to accompanyingdrawings.

As shown in FIG. 1, a system for producing synthetic gas from biomass byhigh temperature gasification comprises: 1. an inlet of biomass; 2. asupercharging feeding system of biomass; 3. a carbonization furnace; 4.a combustible gas pipe connected to a burner nozzle of the carbonizationfurnace; 5. an oxygen pipe connected to the burner nozzle of thecarbonization furnace; 6. a burner nozzle of the carbonization furnace;7. a filter; 8. a combustible gas (functioning as purge gas) pipeconnected to the filter; 9. a pyrolysis gas pipe connected to an outletof the filter; 10. a buffer tank; 11. a pyrolysis gas pipe fortransporting charcoal powder; 12. a pyrolysis gas pipe connected to aburner nozzle of a gasifier; 13. a control valve; 14. a heater; 15. atransport pipe of heated pyrolysis gas; 16. an ejector of charcoalpowder; 17. a transport pipe of a mixture of charcoal powder andpyrolysis gas; 18. an outlet pipe of charcoal; 19. a charcoal cooler;20. a transport pipe of cooled charcoal; 21. a decompression feedingsystem of charcoal; 22. a normal pressure charcoal pipe; 23. apulverizer; 24. a charcoal powder pipe; 25. a normal pressure transportgas pipe; 26. a normal pressure pneumatic conveying system; 27. atransport pipe of a mixture of normal pressure transport gas andcharcoal powder; 28. a supercharging feeding system of charcoal powder;29. a high pressure charcoal powder pipe; 30. a fluidizing device; 31. afluidizing gas pipe; 32. a transport pipe of fluidized charcoal powder;33. an oxygen pipe connected to a burner nozzle of a gasifier; 34. aburner nozzle of a gasifier; 35. a gasifier; 36. a synthetic gas outlet;37. an ash pipe; 38. a transport pipe of deoxygenated and desaltedwater; 39. a saturated vapor pipe; 40. a gas-charging pipe of thesupercharging feeding system of biomass; 41. a gas-discharging pipe ofthe supercharging feeding system of biomass; 42. a gas-charging pipe ofthe decompression feeding system of charcoal; 43. a gas-discharging pipeof the decompression feeding system of charcoal; 44. a gas-charging pipeof the supercharging feeding system of charcoal powder; 45. agas-discharging pipe of the supercharging feeding system of charcoalpowder; 46. a pyrolysis gas pipe connected to an outlet of thecarbonization furnace; and 47. a water wall.

The burner nozzle 6 of the carbonization furnace is connected to thecombustible gas pipe 4 and the oxygen pipe 5 respectively. Along thepipes connecting the charcoal outlet of the carbonization furnace withthe gasifier, the charcoal cooler 19, the decompression feeding systemof charcoal 21, the pulverizer 23, and the supercharging feeding systemof charcoal powder 28 are disposed sequentially. The ejector of charcoalpowder 16 transports the charcoal powder, and connects with thetransport pipe of heated pyrolysis gas and the transport pipe offluidized charcoal powder. On the top of the carbonization furnace theredisposed an outlet of pyrolysis gas which is connected to the gasifier.The filter 7 is disposed at the outlet of pyrolysis gas. An inlet ofpurge gas of the filter 7 is connected to the combustible gas pipe 8.

Dried biomass is put into the supercharging feeding system of biomass 2via the inlet of biomass 1, and then transported to the carbonizationfurnace 3 by pneumatic booster technology. To the carbonization furnace,external combustible gas from the combustible gas pipe 4 and externaloxygen from the oxygen pipe 5 are separately charged. A combustionreaction between the combustible gas and oxygen provides heat forpyrolysis of biomass. The temperature of the carbonization furnace 3 iscontrolled between 400 and 600° C. by adjusting the input amount ofexternal oxygen. By adjusting the input amount of the externalcombustible gas at between 1 and 5 times that required for a completecombustion with oxygen, the temperature of the burner nozzle of thecarbonization furnace can be controlled less than 1800° C. The productsof the carbonization furnace 3 are pyrolysis gas comprising CO, H₂, CO₂,H₂O, and CH₄ and charcoal. The crude pyrolysis gas enters the filter 7via the pyrolysis gas pipe 46 and is filtered, and solid particlescontaining carbon return to the carbonization furnace 3 via thepyrolysis gas pipe 46. The purified pyrolysis gas enters the buffer tank10 via the pyrolysis gas pipe 9 connected to an outlet of the filter 7.

Part of purified pyrolysis gas from the buffer tank 10 enters the heater14 via the pyrolysis gas pipe transporting charcoal powder 11 and thecontrol valve 13. The pyrolysis gas transporting charcoal powder isheated to between 550 and 650° C. and enters the ejector of charcoalpowder 16 via the transport pipe of heated pyrolysis gas 15. Thesolid-gas ratio in the transport pipe of a mixture of charcoal powderand pyrolysis gas 17 is controlled between 0.03 and 0.45 m³/m³ byadjusting the opening of the control valve 13.

The other part of purified pyrolysis gas from the buffer tank 10 via thepyrolysis gas pipe 12 connected to the burner nozzle of the gasifier andoxygen via the oxygen pipe 33 connected to the burner nozzle 34 of thegasifier enter the burner nozzle of the gasifier. The fluidized charcoalpowder and heated pyrolysis gas are also transported by the transportpipe of a mixture of charcoal powder and pyrolysis gas 17 into theburner nozzle 34 of the gasifier 35. High temperature gasificationreaction happens in the gasifier. By adjusting the input amount of theexternal oxygen and the heat exchange of the water wall 47 havingdeoxygenated and desalted water, the temperature of the synthetic gasoutlet 36 is controlled between 1200 and 1600° C. The gasificationproducts mainly comprise CO, H₂, a small amount of CO₂ and H₂O, andlittle CH₄. The deoxygenated and desalted water in the water wall 47absorbs heat and transforms into sub-high pressure saturated water vaporwhich is discharged into the saturated vapor pipe 39. Ash producedduring gasification is discharged into the ash pipe 37.

The charcoal produced in the carbonization furnace 3 is cooled by thecharcoal cooler 19 to a working temperature of the decompression feedingsystem of charcoal 21, decompressed therein, pulverized by thepulverizer 23, and transferred to the normal pressure pneumaticconveying system 26 via the charcoal powder pipe 24. The normal pressuretransport gas (CO₂ or N₂) pipe 25 transports the charcoal powder to thesupercharging feeding system of charcoal powder 28. By pneumatic boostertechnology, the pressure of the charcoal powder is enhanced by thesupercharging feeding system of charcoal powder 28 to a working pressureof the gasifier 35. The high pressure charcoal powder enters thefluidizing device 30 via the high pressure charcoal powder pipe 29, andis fluidized by external combustible gas from the fluidizing gas pipe31. The fluidized charcoal powder enters the ejector of charcoal powder16 and subsequently transported into the gasifier 35.

EXAMPLE 1

Take wood as a raw material of biomass. The elemental composition andcharacteristic data of the dried wood are listed in Table 1.

TABLE 1 Elemental composition and characteristic data of the dried woodItems Symbol Unit Value Carbon C_(ar) % (Kg/Kg) 39.43 Hydrogen H_(ar) %(Kg/Kg) 5.21 Oxygen O_(ar) % (Kg/Kg) 38.36 Nitrogen N_(ar) % (Kg/Kg)0.15 Sulfur S_(ar) % (Kg/Kg) 0.21 Chlorine Cl_(ar) % (Kg/Kg) 0.00 AshA_(ar) % (Kg/Kg) 5.00 Moisture M_(ar) % (Kg/Kg) 11.64 Ash fusion pointFT ° C. 1436 Low heat value LHV MJ/Kg 14.75

Take natural gas as external combustible gas. The elemental compositionand characteristic data of the external combustible gas are listed inTable 2.

TABLE 2 Components and characteristic data of natural gas ComponentsValue CH₄ 91.746% C₂H₆ 4.480% C₃H₈ 2.257% CO₂ 0.070% O₂ 0.040% N₂ 1.406%H₂S concentration (mg/Nm³) 20.00 Low heat value (kcal/m³) 9000.8

The main operating conditions are set as follows:

1) The transportation amount of biomass 1 into the carbonization furnace3 via the supercharging feeding system of biomass 2 is 4.07 Kg/s;

2) The pressure of the carbonization furnace 3 is 3.1 Mpa, and thetemperature is 500° C.;

3) The input amount of the external combustible gas (mole) is 2 timesthat required for a complete combustion with the input oxygen;

4) The heating rate of pyrolysis of the biomass in the carbonizationfurnace 3 is 50° C./s;

5) The charcoal is cooled by the charcoal cooler 19 to 80° C.;

6) The pyrolysis gas is heated by the heater 14 to 600° C.;

7) The solid-gas ratio in the transport pipe of a mixture of charcoalpowder and pyrolysis gas 17 is 0.03 m³/m³; and

8) The pressure of the gasifier 35 is 3.0 Mpa, and the temperature is1300° C.

Based on the above conditions, the main flow rate and performanceparameters of the system are as follows:

1) The mass flow rate of the external combustible gas (40° C.) enteringthe carbonization furnace 3 is 0.28 Kg/s;

2) The mass flow rate of the external oxygen (160° C.) entering thecarbonization furnace 3 is 0.63 Kg/s;

3) The flame temperature of the burner nozzle 6 of the carbonizationfurnace is 1800° C.;

4) The total weight of the pyrolysis gas produced in the carbonizationfurnace 3 is 3.69 Kg/s;

5) The total weight of the charcoal produced in the carbonizationfurnace 3 is 1.19 Kg/s;

6) The combustible gas which is transported by the fluidizing gas pipe31 and used for fluidizing the charcoal powder has a temperature of 300°C. and a mass flow rate of 0.03 Kg/s;

7) The mass flow rate of the pyrolysis gas used for transportingcharcoal powder in the pyrolysis gas pipe 11 is 0.89 Kg/s;

8) The mass flow rate of the mixed gas in the transport pipe of amixture of charcoal powder and pyrolysis gas 17 is 2.1 Kg/s;

9) The mass flow rate of the pyrolysis gas in the pyrolysis gas pipe 12connected to the burner nozzle of the gasifier 35 is 2.8 Kg/s;

10) The external oxygen transported into the gasifier 35 by the oxygenpipe 33 connected to the burner nozzle of the gasifier has a temperatureof 160° C. and a mass flow rate of 1.5 Kg/s;

11) The total weight of the synthetic gas from the synthetic gas outlet36 is 6.5 Kg/s, and the dry basis of CO and H₂ is 87.2%; and

12) The carbon conversion rate of the system is 99.9%, and oxygenconsumption of effective synthetic gas is 0.3 mol/mol.

EXAMPLE 2

Take wood as a raw material of biomass (as shown in Table 1). Takenatural gas as external combustible gas (as shown in Table 2). Thetemperature of the carbonization furnace 3 is 600° C. The heating rateof pyrolysis of the biomass in the carbonization furnace 3 is 100° C./s.Other operating conditions are the same as that in Example 1.

Based on the above conditions, the main flow rate and performanceparameters of the system are as follows:

1) The mass flow rate of the external combustible gas (40° C.) enteringthe carbonization furnace 3 is 0.33 Kg/s;

2) The mass flow rate of the external oxygen (160° C.) entering thecarbonization furnace 3 is 0.63 Kg/s;

3) The flame temperature of the burner nozzle 6 of the carbonizationfurnace is 1700° C.;

4) The total weight of the pyrolysis gas produced in the carbonizationfurnace 3 is 3.84 Kg/s;

5) The total weight of the charcoal produced in the carbonizationfurnace 3 is 1.19 Kg/s;

6) The combustible gas which is transported by the fluidizing gas pipe31 and used for fluidizing the charcoal powder has a temperature of 300°C. and a mass flow rate of 0.03 Kg/s;

7) The mass flow rate of the pyrolysis gas used for transportingcharcoal powder in the pyrolysis gas pipe 11 is 0.89 Kg/s;

8) The mass flow rate of the mixed gas in the transport pipe of amixture of charcoal powder and pyrolysis gas 17 is 2.1 Kg/s;

9) The mass flow rate of the pyrolysis gas in the pyrolysis gas pipe 12connected to the burner nozzle of the gasifier 35 is 2.96 Kg/s;

10) The oxygen transported into the gasifier 35 by the oxygen pipe 33connected to the burner nozzle of the gasifier has a temperature of 160°C. and a mass flow rate of 1.5 Kg/s;

11) The total weight of the synthetic gas from the synthetic gas outlet36 is 6.6 Kg/s, and the dry basis of CO and H₂ is 87.5%; and

12) The carbon conversion rate of the system is 99.9%, and oxygenconsumption of effective synthetic gas is 0.308 mol/mol.

EXAMPLE 3

Take wood as a raw material of biomass (as shown in Table 1). Takenatural gas as the external combustible gas (as shown in Table 2). Theinput amount of the external combustible gas (mole) is 5 times thatrequired for a complete combustion with the input oxygen. Otheroperating conditions are the same as that in Example 1.

Based on the above conditions, the main flow rate and performanceparameters of the system are as follows:

1) The mass flow rate of the external combustible gas (40° C.) enteringthe carbonization furnace 3 is 0.78 Kg/s;

2) The mass flow rate of the external oxygen (160° C.) entering thecarbonization furnace 3 is 0.604 Kg/s;

3) The flame temperature of the burner nozzle 6 of the carbonizationfurnace is 1200° C.;

4) The total weight of the pyrolysis gas produced in the carbonizationfurnace 3 is 4.3 Kg/s;

5) The total weight of the charcoal produced in the carbonizationfurnace 3 is 1.19 Kg/s;

6) The combustible gas which is transported by the fluidizing gas pipe31 and used for fluidizing the charcoal powder has a temperature of 300°C. and a mass flow rate of 0.02 Kg/s;

7) The mass flow rate of the pyrolysis gas used for transportingcharcoal powder in the pyrolysis gas pipe 11 is 0.89 Kg/s;

8) The mass flow rate of the mixed gas in the transport pipe of amixture of charcoal powder and pyrolysis gas 17 is 2.1 Kg/s;

9) The mass flow rate of the pyrolysis gas in the pyrolysis gas pipe 12connected to the burner nozzle of the gasifier 35 is 3.4 Kg/s;

10) The external oxygen transported into the gasifier 35 by the oxygenpipe 33 connected to the burner nozzle of the gasifier has a temperatureof 160° C. and a mass flow rate of 2.05 Kg/s;

11) The total weight of the synthetic gas from the synthetic gas outlet36 is 7.6 Kg/s, and the dry basis of CO and H₂ is 90.4%; and

12) The carbon conversion rate of the system is 99.9%, and oxygenconsumption of effective synthetic gas is 0.295 mol/mol.

EXAMPLE 4

Take wood as a raw material of biomass (as shown in Table 1). Takenatural gas as external combustible gas (as shown in Table 2). Thetemperature of the carbonization furnace 3 is 400° C. The charcoal iscooled by the charcoal cooler 19 to 200° C. Other operating conditionsare the same as that in Example 1.

Based on the above conditions, the main flow rate and performanceparameters of the system are as follows:

1) The mass flow rate of the external combustible gas (40° C.) enteringthe carbonization furnace 3 is 0.23 Kg/s;

2) The mass flow rate of the external oxygen (160° C.) entering thecarbonization furnace 3 is 0.44 Kg/s;

3) The flame temperature of the burner nozzle 6 of the carbonizationfurnace is 1800° C.;

4) The total weight of the pyrolysis gas produced in the carbonizationfurnace 3 is 3.55 Kg/s;

5) The total weight of the charcoal produced in the carbonizationfurnace 3 is 1.19 Kg/s;

6) The combustible gas which is transported by the fluidizing gas pipe31 and used for fluidizing the charcoal powder has a temperature of 300°C. and a mass flow rate of 0.03 Kg/s;

7) The mass flow rate of the pyrolysis gas used for transportingcharcoal powder in the pyrolysis gas pipe 11 is 0.833 Kg/s;

8) The mass flow rate of the mixed gas in the transport pipe of amixture of charcoal powder and pyrolysis gas 17 is 2.04 Kg/s;

9) The mass flow rate of the pyrolysis gas in the pyrolysis gas pipe 12connected to the burner nozzle of the gasifier 35 is 2.72 Kg/s;

10) The oxygen transported into the gasifier 35 by the oxygen pipe 33connected to the burner nozzle of the gasifier has a temperature of 160°C. and a mass flow rate of 1.5 Kg/s;

11) The total weight of the synthetic gas from the synthetic gas outlet36 is 6.3 Kg/s, and the dry basis of CO and H₂ is 87.1%; and

12) The carbon conversion rate of the system is 99.9%, and oxygenconsumption of effective synthetic gas is 0.3 mol/mol.

EXAMPLE 5

Take wood as a raw material of biomass (as shown in Table 1). Takenatural gas as the external combustible gas (as shown in Table 2). Thetemperature of the pyrolysis gas is heated by the heater 14 to 650° C.The solid-gas ratio in the transport pipe of a mixture of charcoalpowder and pyrolysis gas 17 is 0.45 m³/m³. Other operating conditionsare the same as that in Example 1.

Based on the above conditions, the main flow rate and performanceparameters of the system are as follows:

1) The mass flow rate of the pyrolysis gas used for transportingcharcoal powder in the pyrolysis gas pipe 11 is 0.63 Kg/s;

2) The mass flow rate of the mixed gas in the transport pipe of amixture of charcoal powder and pyrolysis gas 17 is 1.8 Kg/s;

3) The mass flow rate of the pyrolysis gas in the pyrolysis gas pipe 12connected to the burner nozzle of the gasifier 35 is 3.1 Kg/s;

4) The oxygen transported into the gasifier 35 by the oxygen pipe 33connected to the burner nozzle of the gasifier has a temperature of 160°C. and a mass flow rate of 1.5 Kg/s;

5) The total weight of the synthetic gas from the synthetic gas outlet36 is 6.5 Kg/s, and the dry basis of CO and H₂ is 87.2%; and

6) The carbon conversion rate of the system is 99.9%, and oxygenconsumption of effective synthetic gas is 0.3 mol/mol.

Results analysis

1. The Effect of Temperature of Carbonization Furnace on the Results

When the carbonization temperature is less than 400° C., the producedpyrolysis gas contains too much tar, which may result in thecondensation of the pyrolysis gas and affect the transportation ofcharcoal powder. When the carbonization temperature is more than 600°C., ordinary alloy steel materials cannot bear such high temperature,but specific alloy material will increase the cost of the carbonizationfurnace.

2. The Effect of Input Amount of External Combustible Gas on the Results

If the input amount of the external combustible gas (mole) is equal tothat required for a complete combustion with the input oxygen, acomplete reaction between the combustible gas and the input oxygenhappens, and the flame temperature of the burner nozzle of thecarbonization furnace will be more than 2000° C. Working for a long timeat such a high temperature will destroy the internal mechanicalcomponents of the carbonization furnace, and even lead to safetyaccident. With the increasing charging of the external combustible gas,the flame temperature of the burner nozzle of the carbonization furnacewill decrease. When the input amount of the external combustible gas(mole) is 5 times that required for a complete combustion with the inputoxygen, the flame temperature of the burner nozzle of the carbonizationfurnace will decrease to 1200° C. If the input amount of the externalcombustible gas is further increased, the flame temperature of theburner nozzle of the carbonization furnace will decrease accordingly,which increases the gas velocity of the outlet of the burner nozzle andleads to unstable combustion. Furthermore, increased gas velocity of theoutlet of the burner nozzle of the carbonization furnace will lead tothe sharp increase of CH₄ content at the outlet of the gasifier. Inorder to reduce to the content of CH₄, the gasification temperatureneeds enhancing, which will lead to a high investment cost on thegasifier.

3. The Effect of Solid-Gas Ratio in the Transport Pipe of a Mixture ofCharcoal Powder and Pyrolysis Gas on the Results:

When the solid-gas ratio is less than 0.03 m³/m³, the pyrolysis gas fortransporting charcoal powder accounts for a large proportion, and thepyrolysis gas reacting with oxygen in the gasifier accounts for a smallproportion, which will affect the stable operation of the burner nozzleof the gasifier. When the solid-gas ratio is more than 0.45 m³/m³, thecharcoal powder may subside or block during transportation, which willlead to the fluctuation of charcoal powder amount and affect the stableoperation of the burner nozzle of the gasifier.

4. The Effect of the Outlet Temperature of the Charcoal Cooler on theResults

When the charcoal temperature at the outlet of the charcoal cooler isless than 60° C., the area and volume for heat exchange of the coolermust be large, which means a high cost. Furthermore, the lower thecharcoal temperature, the lower the system efficiency. When the charcoaltemperature at the outlet of the charcoal cooler is more than 200° C.,some devices of the decompression feeding system of charcoal may not runsmoothly.

While particular embodiments of the invention have been shown anddescribed, it will be obvious to those skilled in the art that changesand modifications may be made without departing from the invention inits broader aspects, and therefore, the aim in the appended claims is tocover all such changes and modifications as fall within the true spiritand scope of the invention.

1. A method for producing synthetic gas from biomass by high temperature gasification, the method comprising: (a) feeding biomass to a carbonization furnace; (b) carbonizing the biomass in said carbonization furnace to produce pyrolysis gas and charcoal; (c) pulverizing the charcoal into charcoal powder; and (d) transporting the charcoal powder via a transportation pipe to a gasifier for gasification, wherein the pyrolysis gas produced in said carbonization furnace is used as a carrier gas to transport the charcoal powder to said gasifier; and charcoal powder transportation is controlled by controlling the amount of the pyrolysis gas.
 2. The method of claim 1, wherein the ratio of the charcoal powder to the pyrolysis gas in said transportation pipe is controlled at between 0.03 and 0.45 m³/m³.
 3. The method of claim 2, wherein the pyrolysis gas produced by said carbonization furnace is filtered, and is utilized for transporting said charcoal powder as the temperature of the pyrolysis gas is raised to 550-650° C.
 4. The method of claim 2, wherein prior to pulverizing the charcoal into charcoal powder, the charcoal at an outlet of said carbonization furnace is cooled to 60-200° C. by a cooler, and reduced to a normal pressure by a decompression feeding system of charcoal.
 5. The method of claim 2, further comprising fluidizing the charcoal powder by an external combustible gas before the charcoal powder is transported to said gasifier.
 6. The method of claim 2, wherein carbonizing the biomass is carried out by combustion of an external combustible gas and oxygen in said carbonization furnace; a temperature of a burner nozzle of said carbonization furnace is controlled by adjusting the ratio of an input amount of the external combustible gas to an input amount of oxygen; and a temperature of said carbonization furnace is controlled by adjusting the input amount of oxygen.
 7. The method of claim 6, wherein the temperature of said carbonization furnace is controlled at between 400° C. and 600° C. by adjusting the input amount of oxygen, and the temperature of a burner nozzle of said carbonization furnace is controlled at between 1200° C. and 1800° C. by adjusting the input amount of the external combustible gas at between more than 1 and less than 5 times that of the input amount that is required for a complete combustion with oxygen.
 8. The method of claim 1, wherein the pyrolysis gas produced by said carbonization furnace is filtered, and is utilized for transporting the charcoal powder as the temperature of the pyrolysis gas is raised to 550-650° C.
 9. The method of claim 1, wherein prior to pulverizing the charcoal into charcoal powder, the charcoal at an outlet of said carbonization furnace is cooled to 60-200° C. by a cooler, and reduced to a normal pressure by a decompression feeding system of charcoal.
 10. The method of claim 1, further comprising fluidizing the charcoal powder by an external combustible gas before the charcoal powder is transported to said gasifier.
 11. The method of claim 1, wherein carbonizing the biomass is carried out by combustion of an external combustible gas and oxygen in said carbonization furnace; a temperature of a burner nozzle of said carbonization furnace is controlled by adjusting the ratio of an input amount of the external combustible gas to an input amount of oxygen; and a temperature of said carbonization furnace is controlled by adjusting the input amount of oxygen.
 12. The method of claim 11, wherein the temperature of said carbonization furnace is controlled at between 400° C. and 600° C. by adjusting the input amount of oxygen, and the temperature of a burner nozzle of said carbonization furnace is controlled at between 1200° C. and 1800° C. by adjusting the input amount of the external combustible gas at between more than 1 and less than 5 times that of the input amount that is required for a complete combustion with oxygen. 